1. Field of the Invention
The present invention relates to a numerical controller for controlling a machine tool, and more particularly, to a numerical controller for controlling axes of a machine tool based on data stored in a table.
2. Description of the Related Art
There is conventionally known a numerical controller having a function (path-table operation function) such that tabular data (path tables) in which the respective positions of axes as control objects are set based on time or the position of a spindle or axis are successively read as the axes are driven, not the command by the block of NC program. Based on this path-table operation function, a tool can be freely operated without regard to a machining program, thus ensuring a reduction in machining time and higher-performance machining.
A numerical control method in which the positional relationships between time (or rotation angle) and movable axes are stored as numerical control data is disclosed in, for example, Japanese Patent Application Laid-Open No. 59-177604 as a related prior art technique. The time (or rotation angle) is monitored, and numerical control data corresponding to the time (or rotation angle) is output to the movable axes every time the time (or rotation angle) reaches a time (or rotation angle) commanded by the numerical control data.
Further, a numerical controller provided with a data table for storing command positions of X- and A-axes compared with a reference position is disclosed in Japanese Patent Application Laid-Open No. 2003-303005. The reference position is obtained by multiplying a value in a counter for counting reference pulses by an override value. Based on this obtained reference position, the command positions of the X- and Z-axes stored in the data table are output to control the X- and Z-axes synchronously. By doing this, overriding can be performed even in controlling the drive based on the data stored in the data table. Further, a command may be issued such as to connect the command positions by means of a straight line, quadric curve, or cubic curve, and in addition, to allow an auxiliary function to be commanded.
In the case of a large gantry machine shown in FIG. 1 where a gantry is driven by the X- and A-axes, these axes are controlled so as to operate with the same route pattern. In running the large gantry machine based on tabular data (path tables), it is necessary to provide path tables for the X- and A-axes, individually, although the path tables have the same contents.
In an operation based on conventional tabular data (path tables), as described above, it is necessary to create the tabular data for each movable axis. The tabular data contain the respective positions of the movable axes based on time or the position of an axis (or spindle) and movable axis names. A memory in the numerical controller should be preloaded with the created tabular data.
Therefore, even in the case of FIG. 1 where the movable axes (X- and A-axes) are commanded to have the same route pattern (see FIGS. 2 and 3), for example, the tabular data (path tables) that contain the respective positions of the movable axes based on time or the position of an axis (or spindle) and are different only in axis name have to be created individually for the X- and A-axes (see FIGS. 4 and 5).
FIG. 6 shows an example of an NC program for starting tabular data (path tables).
In FIG. 6, “M700” of a block “M700Q1000” represents an M code for starting a path-table operation. “Q1000” represents each 1000th path table. When a command from “M700Q1000” is executed, a 1000th path table (FIG. 4) for the X-axis and a 1000th path table (FIG. 5) for the A-axis are started to operate the X- and A-axes.
FIG. 4 shows an example of a path table for the X-axis. “1000_X” in this path table represents the 1000th path table for the X-axis. Thus, the “1000th” path table and the “X-axis” as a controlled axis are assigned in this example. Further, the “position” of the X-axis as the controlled axis is correlated with a “reference value” for time or the position of a reference spindle.
FIG. 5 shows an example of a path table for the A-axis. “1000_A” in this path table represents the 1000th path table for the A-axis. Thus, the “1000th” path table and the “A-axis” as a controlled axis are assigned in this example. Further, the “position” of the A-axis as the controlled axis is correlated with a “reference value” for time or the position of a reference spindle.
The data “reference value” and “position” in the path table for the A-axis in FIG. 5 are the same as those in the path table for the X-axis in FIG. 4. Thus, the two identical tabular data (path tables) must be stored in the memory of the numerical controller, so that the memory capacity for the storage inevitably gets larger.